Aspasia Marina, located on Front Street in South Portland, has been affected by increased sediments that make berthing difficult for fisherman in the area. Courtesy David Clarke

SOUTH PORTLAND — Officials say the city’s waterfront will likely be the location of a $30 million dredging project, tentatively set to begin in 2021, that may eliminate toxic sediment from the bed of Casco Bay.

Areas in the city’s waterfront affected by sediment build-up include Aspasia Marina, Sunset Marina, Breakwater Marina and Port Harbor Marine. Nearly 250 boat are located on the waterfront, with 150 of those leased by South Portland residents and 100 leased by non-residents.

The permit from the Portland Harbor Commission allows for dredging 30 piers and wharves throughout South Portland and Portland.

The plan, which has never been used in Maine, includes creating an underwater pit to house toxic sediment on the floor of the harbor and capping it with sand.

A chart that shows how toxic sediments will be placed in an excavated pit to be located in South Portland. Contributed

Pier owners have lost berths because the water isn’t deep enough for fishermen and other boaters to keep their vessels afloat. Silt deposits continue to grow each year, and the problem has only gotten worse.

“I’m running out of water underneath my boat,” lobsterman Will Copper Smith told the city council Sept. 17. “It used to be that it floated all the time and when there were low tides I could let it sit there and get a cup of coffee and it would be fine. It’s not that way anymore.”

“We’re losing 6 inches to a foot every year on the Portland side. We need to get this dredged and this is the most environmentally friendly way to attack this,” said Parker Pool, whose family owns and operates Union Wharf in Portland. “It needs to be solved for both Portland and South Portland … they’ve done their homework and know how to do this safely.”

A $350,000 federal grant will offset some expenses but additional funding is expected to come from a variety of sources. Portland Waterfront Coordinator Bill Needelman said they plan to use federal and state money to subsidize the cost to pier owners. Money will also come from the BUILD grant application, yet to be submitted, and transportation funds.

What isn’t covered by grants and other funding may be paid for by tipping fees charged to those leasing berths. The tipping fees will be based on sediment volume moved. Should the tipping fees not cover the costs, it may be up to the taxpayers.

Hopefully, Needelman explained, a lot of funds won’t be requested from marina owners as long as grant funding is approved.

“We’re trying very hard not to reach into local taxpayer pockets,” Needelman said.

Required permits will be completed in November, with the hope of approval by May 2020. If all goes according to plan, harbor dredging is scheduled to begin in 2021 and estimated to be completed by 2026.

According to Needelman, data collected by Stantec Inc. shows sediment that’s accumulated for about 70 years has closed off 10-30% of the berths along the central waterfront.

While sediment does accumulate naturally, he said, it can be exacerbated by overflow from combined stormwater and sewage overflows. The harbor’s history of contamination from heavy industry on the waterfront also plays a huge role in the toxicity of sediments.

The contaminated sediment cannot be dumped on land or farther out at sea, Needelman said.

The underwater pit would be located between the Coast Guard station on High Street and the South Port Marine on Ocean Street, capped about 2 feet below the surface at the depth of low tide. Needelman said South Portland was the best location to place the cell because it would be less likely to impact fishermen and marine life in the area.

Upon the completion of dredging, Needelman said, sites will likely be worth more money to marina operators. With improved and expanded berthing and a cleaner environment, he said it’s in the best interest of the city’s to remove human and biological exposure to the sentiments.

Needelman said dredging always takes place in the winter because environmental restrictions are necessary to minimize the impacts on fishery and marine life.

“It is destructive, you are digging up the bottom of the harbor, but its the most environmentally-conscious option we have,” he said. “I can’t promise this won’t be without a degree of disturbance but it will happen at that time of year when the environment can best accommodate that and within the limits of permitting agencies.”